With continuous development of electronic technology, there are more and more cases that users use mobile communication devices to watch multimedia, play games or browse the Internet, for example, in the case of using an electronic terminal to watch multimedia, play games or browse the Internet, the user pays attention to whether a remaining battery capacity of the electronic terminal can support the user to watch multimedia, playing games or browsing the Internet or not, while the current electronic terminal displays the battery power in the form of the number of icon grids or a percentage, which is very impractical for the user. For example, when a user uses an electronic terminal to watch an online movie or network TV, what the user actually cares about is whether the current battery can support him/her to finish the current program or not, without caring how much the battery power is left currently.
When the electronic terminal provides the user with an accurate remaining time, it must meet two requirements, one is an accurate calculation of the remaining capacity of the system power supply, and the other is an accurate detection of a system working current.
Currently, the electronic terminal mainly has the following two schemes to solve the abovementioned two problems:
one scheme is to use a fitting algorithm to estimate the battery capacity depending on to the battery voltage and battery temperature, but for this scheme, an error is relatively large and it is not suitable for applications with high-precision.
The other scheme is to add a sampling resistor in the charging and discharging circuit of the battery, and depending on the system charging and discharging current and the battery temperature acquired from the sampling resistor, and an integral algorithm is used to calculate the battery capacity. With this scheme, the working current range of this sampling resistor must be limited between 5 mA˜2 A, according to the Ohm's law, when maintaining the working voltage of the electronic terminal within the range, the sampling resistor generally uses a resistor with fixed resistance value of 5 milliohms˜100 milliohms, if increasing the resistance value of the sampling resistor at this time, the system power consumption increases correspondingly, which has a great effect on the current accuracy, however, if the current accuracy is not good enough, it greatly affects the accuracy of the calculated electric quantity, and the accuracy of the calculated electric quantity is not good enough.